The present invention relates to improvements in the automatic arc welding processes and more particularly to a method of multiple electrode gas shielded arc welding.
The submerged arc welding process and the gas shielded arc welding process are the popular welding processes among the known automatic arc welding processes. A disadvantage of the submerged arc welding process in which a flux is used to serve the purposes of deoxidization and addition of alloying elements is that the removal of the flux is troublesome, the flux is expensive and the equipment tends to become bulky and expensive since it requires additional devices such as a flux feeding device. In the latter gas shielded arc welding process, the work is arc welded by using a pure gas such as argon or carbon dioxide gas or a mixed gas such as a mixture of argon with carbon dioxide gas or oxygen to exclude the entry of the air, particularly oxygen and nitrogen and therefore this welding process has the disadvantage of slow welding speed though it is free from the above-mentioned deficiencies of the submerged arc welding process. In view of these circumstances, the welding processes have been used frequently in which two or more electrodes are arranged in a straight row along the welding seam line of a piece or pieces to be welded for continuously accomplishing the desired multi-layer welding with the multiple electrodes. While this type of process has the effect of improving the welding efficiency to some extent, there is a serious disadvantage that there is non-uniformity of the properties among the different positions of the weld metal, particularly the impact properties at these positions differ considerably from one another.